my 2 cents:

the "truth" (i use the term loosely because it's quite subjective) probably lies somewhere in the middle.

Your friend's wife probably shouldn't have escalated and called you a cruel, sadistic redneck, but from what i read (judging from limited information) you probably provoked a little bit with the "better shut the fuck up" comment. It's wise to not try and be so confrontational especially with your friend's partners - sometimes it's better to agree to disagree as partners can often complicate relationships between friends.

Onto the actual issue - Even somebody that is pro-gun control (as i am to a degree) would recognise that guns to have necessity in some circumstances - you would have been better served to talk about the ecological impact of failing to cull. (if you didn't already try to that is)